Intermittent engine fault?

[Rudi]

Hi there,

I have an Octavia Mk 2 1.6 petrol (2011) with ca. 35k miles under its belt. For a couple of months it has been suffering from a very intermittent fault (happened four times) whereby the engine dies on me.  Once it happened, almost imperceptibly, while I was driving along (flat road, around 30 mph, engine not under much load) and the engine picked up again almost immediately. On other occasions the engine died at low revs (waiting at traffic lights, zebra crossing, etc) and wouldn't restart until it had been left a short while (10 minutes) or wouldn't restart in my driveway after a short run and [intended] stop (in both cases, the journey that preceded the problem lasted about 25-30 minutes (in town).

 

It had its service and MOT 2 weeks ago: no emission issues reported, sparkplugs were replaced as per schedule. It didn't throw up the problem while in the hands of the garage either.

 

I have a Vgate diagnostic scanner and the only fault code I get from the car is P0420, which points to the catalytic converter or oxygen sensors. Could that cause this problem? Would seem unlikely, but maybe someone knows better...? If not, any other suggestions?

 

Thanks in advance,

 

R.

[Rudi]

I should maybe also say that when the problem isn't happening, the car drives very well - no rough turnover, no bad odours, no odd noises, no alarms or lights on the dashboard.... I just can't rely on the vehicle to get me from A to B, and I assume it is going to get worse. 

 

R.

[Westbury63]

Given the description, sounds to me like your car might well benefit from a good 'Italian tune up'. A decent amount of revs, say 3000+, for a good few miles would be my first attempt. Burn off some deposits from your exhaust sensors if its spending too much time pootling about in town. Use proper branded fuel (just my opinion, but I always found supermarket fuel a false economy) and shot of redex. HTH

[Rudi]

4 hours ago, Westbury63 said:

Given the description, sounds to me like your car might well benefit from a good 'Italian tune up'. A decent amount of revs, say 3000+, for a good few miles would be my first attempt. Burn off some deposits from your exhaust sensors if its spending too much time pootling about in town. Use proper branded fuel (just my opinion, but I always found supermarket fuel a false economy) and shot of redex. HTH

 

Many thanks for that. It certainly does spend most of its time in 4-8 mile trips across town. But would a clogged sensor cause intermittent stalls/failures to start?

 

[Westbury63]

It may well do. By there very nature, intermittent faults are sadly the worst to track down. However, if the exhaust is never getting properly hot, its not burning off deposits that will be left on the sensors and thats where the P0420 fault code is sending you and the use of your car points to it. A regular trip up and down the M8 really would do your car the world of good, cars do not respond at all well to low mileage short runs.

 

The fault code does also suggest leak in the intake system. Have a good look at all of the intake pipes, feel for cracks/tears that are not abvious to the eye. I also recall odd random splutter from my 1.6MPi, cured by a replacement coil pack.

 

Perhaps someone near you has VAG COM and can run a proper scan to see if there are any other codes that your generic tool is not picking up. The forum has a search facility for members near you IIRC.

 

Couple of links for you:

http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056

https://skoda.7zap.com/en/cz/octavia/oct/2011-252/

[LEricG]

On 21/05/2019 at 22:56, Rudi said:

On 21/05/2019 at 22:56, Rudi said:

For a couple of months it has been suffering from a very intermittent fault (happened four times) whereby the engine dies on me.  

 

On other occasions the engine died at low revs (waiting at traffic lights, zebra crossing, etc) and wouldn't restart until it had been left a short while (10 minutes) 

I have had pretty much the same problem for quite a while now with my Felicia. Many times I had to sit and wait for at least 10 minutes, after nipping into a shop, before it would start again. and was going to post a request for help, but decided to search the forum first and found this post. 

I also use my car almost exclusively for short stop/start journeys. 

After a couple of 'burns' for a few miles along the A46 at 3000 - 4000 revs (got it up to 86mph before progress was impeded by some clown pulling out of the inside lane in front of me) the problem seems to be cured, though occasionally the engine will still die when idling. 

Sound advice from Westbury63, thanks. 

I will now be giving it a regular routine maintenance run to burn off the deposits. 

[Rudi]

Thanks LEricG. To follow up: I took Westbury63's advice and took the car on a 60-odd mile run down the A1. Kept the revs between 3-4k as recommended. Also topped up with 'super' formula petrol. All was good, car ran faultlessly, as indeed it did for the next two weeks which involved just a few runs in town (5-8 miles each), total mileage probably less than 25. Today I drove to my daughter's flat (around 5 miles, in town) stayed there for around two hours, got back in the car - and it wouldn't start. Engine turns in the starter motor, just doesn't 'catch', same as before. Took the key out of the ignition, waited two minutes, tried again - it started first time. 😌

 

Was wondering if I should disconnect the battery for a day or two (I have the radio code) to let the EMS completely re-set, which was suggested to me by someone at my work...

[LEricG]

On 23/06/2019 at 21:50, Rudi said:

Was wondering if I should disconnect the battery for a day or two (I have the radio code) to let the EMS completely re-set, which was suggested to me by someone at my work...

That's out of my sphere of knowledge I'm afraid. I never progressed from carbs and distributes, and then only basic. 

[Westbury63]

Hi Rudi. Pleased to hear the italian tune up helped. I never just do a short run in my cars. Even if I've just got a short journey to do, such as supermarket shopping, the car will get a decent 10 mile run once started. Something Ive done for 30+yrs and has proven to my mind at least, that use benefits a car. 

 

Sorry to hear of the random problem, they're so frustrating. Perhaps another fault code read would be beneficial? I purchsed a cheapie of ebay for this purpose.

 

If I were you, I would now be checking the HT leads. On the MPi engine, no2 + 3 lead are tricky to get to and may not be 100% seated correctly. That said, do you know when the spark plugs were last changed? Again, no2+3 are tricky to replace due to the inlet manifold and may have been 'overlooked' by a time poor technician. Also worth checking the obvious electrical connectors such as the MAF are properly connected. I would also 100% be checking & cleaning the earth strap.

 

Basic stuff that you can do before needing to pay labour rates at a garage. Not sure I would be disconnecting the battery for a week however. HTH

 

 

[Jevpls]

Well, it's a petrol car with a 5 speed gearbox. I've driven 1,6 Octavia (MPI, this might be FSI) and ~100 or 105 kph it was already like 3500 rpm.